Which absorbs damage first: temporary hit points or Arcane Ward?

Question

Suppose I am an abjuration wizard with 3 temporary hit points and 5 hit points on my Arcane Ward. If I take damage, which hit points absorb damage first? For example, what will be my status after taking 4 damage? Will this damage force me to make a saving throw to maintain concentration? (In case it matters, assume that I have 30 hit points.)

As written, it seems that both effects trigger simultaneously (emphasis added):

Arcane Ward:

Whenever you take damage, the ward takes the damage instead.

Temporary hit points:

When you have temporary hit points and take damage, the temporary hit points are lost first, and any leftover damage carries over to your normal hit points.

Answer 1

The ward takes the damage first regardless of what order they apply

The following Q/A establishes that damage to your temporary hit points still counts as you taking damage and with that knowledge, there are two possible cases:

• Is a concentration check required when temporary hit points absorb all the damage?

  1. The ward clause applies first; in this case you are no longer taking damage so the temporary hit points won't do anything.

  2. The temporary hit points clause applies first; in this case you are taking damage so the ward's clause will now apply, taking that damage instead.

This is also supported by lead game designer Jeremy Crawford in an unofficial ruling (a tweet):

Q. How do the Abjurer's Arcane Ward and Temporary Hitpoints interact? Do they stack? If so, which is depleted first?

A. An abjurer's Arcane Ward takes damage first. Any leftover damage is taken by temporary hp, then normal hp.

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It's different if you believe temporary hit points taking damage doesn't count as you taking damage

This stance is taken by the second answer to the initially linked question and in this case, the order will matter because either clause applying will result in you no longer taking damage.

In this case I would default to the optional rule from Xanathar's Guide to Everything for resolving simultaneous effects:

In rare cases, effects can happen at the same time, especially at the start or end of a creature's turn. If two or more things happen at the same time on a character or monster's turn, the person at the game table - whether player or DM - who controls that creature decides the order in which those things happen.

Either way, you never make a concentration check

Note that under either belief, no matter what, a concentration check will not be made. In the first account the ward is always taking the damage, not you; in the second account either the ward of the temporary hit points take the damage and neither would count as you taking damage.

Answer 2

It's your choice(*)

From Xanathar's Guide to Everything, page 77:

In rare cases, effects can happen at the same time, especially at the start or end of a creature's turn. If two or more things happen at the same time on a character or monster's turn, the person at the game table - whether player or DM - who controls that creature decides the order in which those things happen.

Here we have two instances of "X happens when you take damage", so you can choose which one happens first.

* However...

When you redirect the damage to your Arcane Ward, you no longer take that damage ("(...) the ward takes the damage instead."), which means you do not have to make Concentration checks. Technically, this means that temporary hit points are no longer in consideration, since you're no longer taking damage, unless the Ward has less hp than the damage redirected to it.

Temporary hit points, on the other hand, are granted to your character and are a part of that character ("[Some abilities] confer temporary hit points to a creature."), so damage to temporary hit points is still damage to the character, and calls for Concentration checks.

Answer 3

Arcane Ward

The arcane ward is a magic barrier that takes damage like a shield. You have to go through this barrier before you can take physical damage. Once you go through this barrier the temporary hp gets affected.